24 SEX 



the water and feeds in part at least like a 

 green plant. But let us consider its repro- 

 ductive relations. 



It occasionally happens that a component 

 unit of the ball of cells may become repro- 

 ductive and divide to form a daughter-colony 

 (see Fig. 4A) without more ado. This is an 

 almost vegetative way of multiplying, at 

 least a parthenogenetic one. But in other 



FIG. 4A. A Volvox colony showing in the interior four 

 daughter-colonies (DC), produced asexually. (After Klein.) 



conditions, when nutrition is checked, a less 

 direct mode of reproduction occurs. Some of 

 the cells in the living ball become large, well- 

 fed elements the ova; others, less anabolic, 

 fade from green to yellow, divide and re- 

 divide into many minute units the sperma- 

 tozoa. Here we see the formation of dimorphic 

 reproductive cells in different parts of the 

 same organism. But we may also find Volvox 

 colonies in which only ova are being produced 



